前言
mybatis開發過程中用到的還是比較多的,之前我用的大多都是註解形式,xml用的不多,所以就用了點時間吧xml格式的也看了下,做了總結在這裏寫下。
開始工作
引入jar包
<dependency><!-- 引入mybits依賴-->
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.1.1</version>
</dependency>
<dependency><!-- mysql連接java包 -->
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
配置文件
#驅動名稱
spring.datasource.driverClassName=com.mysql.jdbc.Driver
#url地址
spring.datasource.url=jdbc:mysql://localhost:3306/poetry?useUnicode=true&characterEncoding=utf-8&&serverTimezone=GMT%2B8
#用戶名
spring.datasource.username=root
#密碼
spring.datasource.password=yu123467.
#掃描實體類路徑
mybatis.type-aliases-package=com.xue.mybitsdemo.entity
#映射文件路徑及名稱
mybatis.mapper-locations:classpath:mapper/*Mapper.xml
#mybats配置文件
mybatis.config-location:classpath:config/mybits-config.xml
測試用表建表語局
CREATE TABLE `student` (
`s_id` INT(11) NOT NULL AUTO_INCREMENT COMMENT '主鍵id',
`s_name` VARCHAR(50) NOT NULL DEFAULT '0' COMMENT '學生姓名',
`s_age` INT(11) NOT NULL DEFAULT '0' COMMENT '學生年齡',
`s_sex` VARCHAR(50) NOT NULL DEFAULT '0' COMMENT '學生性別',
PRIMARY KEY (`s_id`)
)
COMMENT='學生信息表'
ENGINE=InnoDB
;
目錄結構
-- main
--java
--com.xue.mybitsdemo
--dao
--StudentMapper.class
--entity
--StudentEntity.class
--MybitsdemoApplication.class
--resource
--config
mybatis-config.xml
--mapper
StudentMapper.xml
--application.properties
xml格式
mybits-config.xml文件內容
可設置項有很多,更多的戳這裏
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<settings>
<!-- 開啓駝峯匹配 -->
<setting name="mapUnderscoreToCamelCase" value="true" />
</settings>
</configuration>
Mapper開發
package com.xue.mybitsdemo.dao;
import com.xue.mybitsdemo.entity.StudentEntity;
import java.util.List;
public interface StudentMapper {
//根據id獲取一條數據
StudentEntity getOne(Integer id);
//根據多條件獲取一條數據
StudentEntity getOne2(StudentEntity studentEntity);
//獲取全部數據
List<StudentEntity> getAll();
//插入一條數據
void insert(StudentEntity studentEntity);
//刪除一條數據
void deleteOne(Integer id);
//修改一條數據
void update(StudentEntity studentEntity);
}
這些接口需要在映射文件中一一實現,可以在類文件上添加@Mapper註解,很多Mapper的話有點麻煩,推薦直接在啓動類那添加。啓動的時候,就去掃描,自動注入了
@SpringBootApplication
@MapperScan(basePackages= {"com.xue.mybitsdemo.dao"})
public class MybitsdemoApplication {
public static void main(String[] args) {
SpringApplication.run(MybitsdemoApplication.class, args);
}
}
實體類文件
package com.xue.mybitsdemo.entity;
public class StudentEntity {
private Integer id;
private String name;
private Integer age;
private String sex;
public StudentEntity(Integer id, String name, Integer age, String sex) {
this.id = id;
this.name = name;
this.age = age;
this.sex = sex;
}
public StudentEntity(String name, Integer age, String sex) {
this.name = name;
this.age = age;
this.sex = sex;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
@Override
public String toString() {
return "StudentEntity{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
", sex='" + sex + '\'' +
'}';
}
}
添加Student的映射文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.xue.mybitsdemo.dao.StudentMapper">
<resultMap id="studentMap" type="StudentEntity">
<id column="s_id" property="id" jdbcType="BIGINT"/>
<result column="s_name" property="name"/>
<result column="s_age" property="age"/>
<result column="s_sex" property="sex"/>
</resultMap>
<!-- <insert id="insert" useGeneratedKeys="true"-->
<!-- keyProperty="id" parameterType="StudentEntity" >-->
<!-- insert into student (s_name,s_age,s_sex)-->
<!-- values (#{name},#{age},#{sex})-->
<!-- </insert>-->
<insert id="insert" parameterType="StudentEntity">
insert into student (s_name,s_age,s_sex)
values (#{name},#{age},#{sex})
</insert>
<select id="getAll" resultMap="studentMap">
select s_id,s_name,s_age,s_sex from student
</select>
<select id="getOne" parameterType="Integer" resultMap="studentMap">
select s_id,s_name,s_age,s_sex from student where s_id = #{id}
</select>
<select id="getOne2" parameterType="StudentEntity" resultMap="studentMap">
select s_id,s_name,s_age,s_sex from student
<where>
<if test="id != null">
s_id=#{id}
</if>
<if test="name != null">
AND s_name=#{name}
</if>
<if test="age != null">
AND s_age=#{age}
</if>
<if test="sex != null">
AND s_sex=#{sex}
</if>
</where>
</select>
<delete id="deleteOne" parameterType="Integer">
delete from student where s_id = #{id}
</delete>
<!-- <update id="update" parameterType="StudentEntity">-->
<!-- update student set s_name = #{name},s_age = #{age},s_sex = #{sex} where s_id=#{id}-->
<!-- </update>-->
<update id="update" parameterType="StudentEntity">
update student
<set>
<if test="name != null">s_name=#{name},</if>
<if test="age != null">s_age=#{age},</if>
<if test="sex != null">s_sex=#{sex}</if>
</set>
where s_id=#{id}
</update>
</mapper>
xml詳細解釋
resultMap 自定義返回結果。
主要用於轉換字段,當數據庫的字段和實體類的不一致的時候。其中column屬性是數據庫字段,property屬性是實體類的字段。數據庫裏面的是“s_name”字段,實體類的是“name”字段。當然了,還有更簡單的,那就是數據庫查詢的時候直接 select s_name as name from student。 用resultMap 主要是爲了規範
<select><update><delete><insert>中的id屬性值必須和mapper中的方法名完全一致
parameterType 參數類型
namespace命名空間,可以通過此路徑來調用映射文件。
update,getOne2兩個方法,分別用了<where></where>和<set></set>,這兩個用法就是避免了自己在寫部分條件爲空的邏輯處理過程了。
<where></where> 裏面的邏輯條件至少有一個成立,纔會出現後面的 where column = “value”,否則等於select * from student;沒有後面的where子句
<set></set>也是如此,如果都爲空,也是會報錯的,那是的sql語句大致是這樣
udpate student where column = “value”,所以他們只是簡化了非空的邏輯判斷的sql語句組合寫法,比如不用考慮是不是多個",",還有update字段的時候,是不是多個“AND”,這些mybtis都做好了,直接用就可以了
更多的戳這裏
測試類
@RunWith(SpringRunner.class)
@SpringBootTest(classes = MybitsdemoApplication.class)
public class StudentMapperTest {
@Autowired
private StudentMapper studentMapper;
@Test
public void insertTest() {
//添加數據
StudentEntity studentEntity = new StudentEntity(1, "yu", 24, "male");
StudentEntity studentEntity1 = new StudentEntity(2, "xue", 25, "female");
studentMapper.insert(studentEntity);
studentMapper.insert(studentEntity1);
Assert.assertEquals(2, studentMapper.getAll().size());
//獲取全部數據
List<StudentEntity> studentEntityList = studentMapper.getAll();
for (StudentEntity studentEntitytemp : studentEntityList) {
System.out.println(studentEntitytemp.toString());
}
//根據id獲取數據
StudentEntity studentEntity2 = studentMapper.getOne(2);
System.out.println(studentEntity2.toString());
Assert.assertEquals("xue", studentEntity2.getName());
//update部分數據項
StudentEntity studentEntity3 = new StudentEntity(2, "xueshanshan", null, null);
studentMapper.update(studentEntity3);
//根據實體類獲取一條數據
StudentEntity studentEntity4 = studentMapper.getOne2(studentEntity3);
System.out.println(studentEntity4.toString());
Assert.assertEquals("xueshanshan", studentEntity4.getName());
//刪除數據
studentMapper.deleteOne(2);
Assert.assertEquals(1, studentMapper.getAll().size());
}
}
xml更多的還是適用於複雜的sql語句,各種嵌套查詢等,這些返回結果集中也都有相對應的處理,註解形式的,相較於xml而言,就簡單多了,等我有空了再寫那個。
如果配置過程中有什麼問題,下面留言即可,我看到了會回覆的。